The molecular structure of mammalian procollagen will be studied by physical and chemical methodologies. In vitro culture methods utilizing human foreskin fibroblasts and cloned Chinese hamster lung cells will be employed under conditions limiting proteolytic degradation of procollagen as well as cell free protein synthesis systems. Specific areas to be investigated include the elucidation of the single versus multiple chain models for procollagen, the molecular basis for chain registration, and a probe for the existence of a preprocollagen by the identification of amino terminal signal peptides.